| Residual stresses left in a machined product have a major influence on the quality of the machined part, in particular, its fatigue life. From the literature review on the study of residual stresses induced by machining process, it is clear that the majority of the prior work focus on experimental studies in an effort to understand the nature of residual stress formation. The limited published work on modeling of the residual stress formation in orthogonal machining process, via the use of finite element method (FEM), has shown it to be a feasible approach to study the problem. However, the review of previously used models also indicates several deficiencies, such as the use of chip-workpiece separation criterion, or over-idealized material model, etc. A review of the finite element models established for the chip formation process also indicates the lack of data to model the material behaviors under conditions of large strain, high strain-rate and high temperature commonly encountered in a machining process. A thermal-elastic-viscoplastic finite element model is developed in the current work to study the residual stress formation in an orthogonal machining process. A modified Johnson-Cook material model is used to describe the inelastic material behavior. A rounded cutting tool edge is used in the simulation with the use of a remeshing scheme to simulate the material flow in the vicinity of the cutting tool tip. A new approach is used to improve the accuracy in the hydrostatic stress component calculated from the FEM. Thus, an improvement in the accuracy for the residual stresses is obtained. Case studies are performed to study the influence of sequential cut, cutting conditions, etc. on the residual stress induced by cutting. |
